A body part which is reduced in size and seems to have no function is called worksheet

These body parts are called vestigial structures. Vestigial structures are body parts that are reduced in size, have no apparent function, and thought to be derived from other, ancestral body parts, examples are appendix, wisdom teeth, tail bone, muscles that wiggle ears. They are often homologous to structures that are functioning normally in other species, thus they can be considered evidence for evolution, the process by which beneficial heritable traits arise in populations over an extended period of time.